.. _PySP conversion:

PySP Conversion (Legacy)
=========================

.. note::
   PySP support is maintained for backward compatibility. New projects
   should write a ``scenario_creator`` function directly
   (see :ref:`scenario_creator`) and use ``generic_cylinders.py``
   (see :ref:`generic_cylinders`).

Details
^^^^^^^

To use a PySP model in `mpi-sppy`, the critical step is to instantiate
a ``PySPModel`` object. The API for the class is:

.. automodule:: mpisppy.utils.pysp_model.pysp_model
   :members:
   :undoc-members:
   :show-inheritance:

Once a ``PySPModel`` object and an options dictionary have been
created, an ``ExtensiveForm`` or ``PH`` object can be created using
the ``PySPModel`` object attributes.

As reflected in the API for the ``PySPModel`` class there are many ways
to specify the reference model and scenario tree information in PySP.
A few examples are given in directory ``examples/farmer/from_pysp``.
Here are few notes about these examples:

* They are written mainly to provide code examples.

* How to form the EF is shown in, e.g. ``abstract.py``

For new code, write a ``scenario_creator`` function (as in
``examples/hydro/hydro.py``) and invoke
``mpisppy/generic_cylinders.py`` rather than using ``PySPModel``.
An older hub-and-spoke example that used ``PySPModel`` is preserved
under ``examples/hydro/archive/hydro_cylinders_pysp.py``.